/*
 * Created on Jul 18, 2005
 * Created by Alon Rohter
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package com.aelitis.azureus.core.peermanager.utils;

import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;

import org.gudy.azureus2.core3.util.SystemTime;

/**
 * Handles incoming peer message counting/timing/stats in order to catch and block abusive peers.
 */
public class PeerMessageLimiter {

    private final HashMap message_counts = new HashMap();

    public PeerMessageLimiter() {
        /* nothing */
    }

    /**
     * Add the reception of the given message to time-limited count.
     * 
     * @param message_id
     *            message to count
     * @param max_counts
     *            max counts allowed within the given time limit
     * @param time_limit_ms
     *            time in ms that the count limiting applies
     * @return true if the added count is within acceptable time limits, false if there have been too many counts
     */
    public boolean countIncomingMessage(String message_id, int max_counts, int time_limit_ms) {

        CountData data = (CountData) message_counts.get(message_id);

        if (data == null) { // new message
            data = new CountData(max_counts, time_limit_ms);
            message_counts.put(message_id, data);
        }

        long now = SystemTime.getCurrentTime();

        data.counts.addLast(new Long(now));

        if (data.counts.size() > data.max_counts) { // we've potentially reached our count limit

            long cutoff = now - data.time_limit;

            // prune out any expired counts
            for (Iterator it = data.counts.iterator(); it.hasNext();) {
                long time = ((Long) it.next()).longValue();

                if (time < cutoff) { // this count is older than the limit allows
                    it.remove(); // drop it
                } else { // still within limit
                    break;
                }
            }

            if (data.counts.size() > data.max_counts) { // too many counts within the time limit
                return false; // return error
            }
        }

        return true;
    }

    private static class CountData {
        private final int max_counts;
        private final int time_limit;
        private final LinkedList counts = new LinkedList();

        private CountData(int max_counts, int time_limit) {
            this.max_counts = max_counts;
            this.time_limit = time_limit;
        }
    }

}
